1. Field of the Invention
This invention relates generally to a method and apparatus for transferring digital data between functional circuit elements in video equipment and, more particularly, for efficiently transferring such digital data in television receivers and video tape recorders in an efficient fashion without producing noise interference.
2. Description of the Background
Video and audio equipment that incorporates internal circuit elements and internal buses that can be digitally controlled are well known. For example, U.S. patent application Serial No. 06/751,982, filed June 28, 1985, and assigned to the assignee of the present invention, describes a control arrangement and method for use with electronic equipment having internal bus elements, in which an external computer is connected to the internal bus. The specific arrangement described in the above-identified patent application relates to a television receiver that employs an internal central processing unit, as well as internal bus lines that connect the audio processing circuitry, the video processing circuitry, the video control circuit, and the deflection control circuit, all of which are digitally controlled by the central processing unit. In conventional operation, the central processing unit also controls a tuning circuit in accordance with instructions that are entered by the user by means of a keyboard on the receiver or a remote control unit. These manually entered instructions relating to the tuning and the like are also typically displayed on a visual display element.
The internal bus is also provided with a connector so that a remotely located computer can be connected to the receiver for testing and/or adjusting both during manufacturing or during repair servicing. Similar instructions can also be entered using a remote control unit that communicates with the receiver using the conventional infrared remote control interface.
When the adjustments are being made to the television set using either the internal central processing unit or the externally connected computer, the command data is transferred over the internal bus in synchronization with internally generated clock pulses. The problem is presented then that as the frequency of the clock pulses is increased noise is generated of such a magnitude that radiation interference disturbances appear on the screen of the television receiver. To avoid these noise disturbances or interferences from being visually presented, one solution is to decrease the clock pulse frequency to reduce the noise. Another approach is to transmit the data only during the vertical blanking interval of the video signal, so that any noise interference that is generated can not be visually displayed. Nevertheless, while solving the noise problem, decreasing the clock frequency also severely reduces the data transmission rate and transferring data only during the vertical blanking intervals reduces the data transfer efficiency and requires a longer period of time in order to transmit all of the necessary command data, thus, slowing down the response characteristics of the television set.